Pope Benedict consecrates unfinished Sagrada Famiglia in Barcelona

The Pope sprinkled holy water on the altar before a congregation of more than 6,500 people, where Gaudi's greatest work has been under construction for more than a century, and is not expected to be complete before 2026.

The current chief architect said he hoped the Pope's visit would provide the boost needed to finish the work, which is currently being funded by private donations and visitor’s fees.

"He will bring a message of spirituality and it's a stimulus to finish the work," Jordi Bonet Armengol said.

Following the consecration, the main nave is now open for daily Mass for the first time.

Work began on Barcelona's Sagrada Familia in 1882, based on a design by Francesc de Paula Villar, who envisioned a simple church in a traditional neo-Gothic style.

After resigning in 1883, Gaudi was appointed the lead architect and redesigned the church entirely. His imaginative plans included 18 spires and five naves, with rich decoration and detail.

He once said it was an expression of "the divine history of the salvation of man through Christ incarnate, given to the world by the Virgin Mary".

In 1911, the devout Catholic devoted himself entirely to the project, and spent the next 15 years living and working on site as a virtual recluse, supervising work. Gaudi died in 1926, after being run over by a tram.

Already a Unesco world heritage site visited by millions, it will become the world's tallest church when the 170m (560ft) central tower is erected.

In preparation for the Pope's visit, workers covered the central nave and installed stained-glass windows.

Amid crowds lining the streets to greet the Pope, there was also a protest by about 200 gay activists who staged a "kiss-in".

"We are here to demonstrate against the Pope's visit and call for a change in the mentality of the Catholic institution which still opposes our right to different ways of loving," said one protester, Sergi Diaz.